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<h1>Layout management</h1>

<p>
In this part of the Qyoto C# programming tutorial, we will introduce layout 
managers. 
</p>

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<p>
When we design the GUI of our application, we decide what 
components we will use and how we will organize those components
in the application. To organize our components, we use specialized
non visible objects called layout managers. There are several options in Qyoto.
We can use absolute positioning, built-in layout managers or create a custom layout
manager. We can also visually build the layouts using the Qt Designer. 
</p>

<p>
Qyoto has some important built-in layout managers. The <code>QVBoxLayout</code> 
class lines up widgets vertically. <code>QHBoxLayout</code> lines up widgets 
horizontally. The <code>QGridLayout</code> class lays out widgets in a grid. The 
grid layout is the most flexible layout manager. The box layouts can be nested 
into one another to create complex layouts. 
</p>


<h2>Absolute positioning</h2>

<p>
In most cases, programmers should use layout managers. There are a 
few situations, where we can use absolute positioning. In absolute 
positioning, the programmer specifies the position and the size of 
each widget in pixels. The size and the position of a widget do not 
change, if you resize a window. Applications look different on various 
platforms, and what looks OK on Linux, might not look OK on Mac.
Changing fonts in your application might spoil the layout. If you 
translate your application into another language, you must redo your 
layout. For all these issues, use the absolute positioning only when you
have a reason to do so.
</p>

<pre class="code">
using System;
using QtCore;
using QtGui;

/**
 * ZetCode Qyoto C# tutorial
 *
 * In this program, we lay out widgets
 * using absolute positioning
 *
 * @author Jan Bodnar
 * website zetcode.com
 * last modified October 2012
 */


public class QyotoApp : QWidget 
{
    public QyotoApp() 
    {
        WindowTitle = "Absolute";

        InitUI();

        Resize(300, 280);
        Move(300, 300);
        Show();
    }

    void InitUI() 
    {        
        StyleSheet = "QWidget { background-color: #414141 }";

        QPixmap bardejov = new QPixmap("bardejov.jpg");
        QPixmap rotunda = new QPixmap("rotunda.jpg");
        QPixmap mincol = new QPixmap("mincol.jpg");

        QLabel barLabel = new QLabel(this);
        barLabel.Pixmap = bardejov;
        barLabel.Move(20, 20);

        QLabel rotLabel = new QLabel(this);
        rotLabel.Pixmap = rotunda;
        rotLabel.Move(40, 160);

        QLabel minLabel = new QLabel(this);
        minLabel.Pixmap = mincol;
        minLabel.Move(170, 50);
    }

    [STAThread]
    public static int Main(String[] args) 
    {
        new QApplication(args);
        new QyotoApp();
        return QApplication.Exec();
    }
}
</pre>

<p>
In this example, we show three images using the absolute positioning.
</p>

<pre class="explanation">
StyleSheet = "QWidget { background-color: #414141 }";
</pre>

<p>
The <code>StyleSheet</code> property is used to change the background colour of
the client area of the window.  
</p>

<pre class="explanation">
QLabel barLabel = new QLabel(this);
barLabel.Pixmap = bardejov;
</pre>

<p>
The <code>QLabel</code> widget is used to hold the image. 
</p>

<pre class="explanation">
barLabel.Move(20, 20);
</pre>

<p>
We use the <code>Move()</code> method to position the label on the
window at x=20, y=20. 
</p>

<p>
When we resize the window, the labels retain their initial size. 
</p>

<img src="/img/gui/sharpqyoto/absolute.jpg" alt="Absolute">
<div class="figure">Figure: Absolute positioning</div>


<h2>Buttons example</h2>

<p>
In the following example, we will position two buttons in the bottom right 
corner of the window. 
</p>

<pre class="code">
using System;
using QtCore;
using QtGui;

/**
 * ZetCode Qyoto C# tutorial
 *
 * In this program, use box layouts
 * to position two buttons in the
 * bottom right corner of the window.
 *
 * @author Jan Bodnar
 * website zetcode.com
 * last modified October 2012
 */


public class QyotoApp : QWidget 
{
    public QyotoApp() 
    {
        WindowTitle = "Buttons";

        InitUI();

        Resize(300, 150);
        Move(300, 300);
        Show();
    }

    void InitUI() 
    {    
        QVBoxLayout vbox = new QVBoxLayout(this);
        QHBoxLayout hbox = new QHBoxLayout();

        QPushButton ok = new QPushButton("OK", this);
        QPushButton apply = new QPushButton("Apply", this);

        hbox.AddWidget(ok, 1, AlignmentFlag.AlignRight);
        hbox.AddWidget(apply);

        vbox.AddStretch(1);
        vbox.AddLayout(hbox);
    }

    [STAThread]
    public static int Main(String[] args) 
    {
        new QApplication(args);
        new QyotoApp();
        return QApplication.Exec();
    }
}
</pre>

<p>
We use nested box layouts to get our intended layout. 
</p>

<pre class="explanation">
QVBoxLayout vbox = new QVBoxLayout(this);
QHBoxLayout hbox = new QHBoxLayout();
</pre>

<p>
We use one vertical and one horizontal box. 
</p>

<pre class="explanation">
QPushButton ok = new QPushButton("OK", this);
QPushButton apply = new QPushButton("Apply", this);
</pre>

<p>
These are the two buttons that will go into the bottom
right corner of the window. 
</p>

<pre class="explanation">
hbox.AddWidget(ok, 1, AlignmentFlag.AlignRight);
</pre>

<p>
We put the ok button into the horizontal box. The second parameter is the 
<b>stretch</b> factor. It expands the area allotted to the ok button. It takes 
all available space left. Inside this area, the button is aligned to the right. 
</p>

<pre class="explanation">
vbox.AddStretch(1);
</pre>

<p>
This line creates a vertically expanded white space, which will push the 
horizontal box with the buttons to the bottom. 
</p>

<pre class="explanation">
vbox.AddLayout(hbox);
</pre>

<p>
The horizontal box is nested into the vertical box. 
</p>


<img src="/img/gui/sharpqyoto/buttons.png" alt="Buttons example">
<div class="figure">Figure: Buttons example</div>


<h2>Windows example</h2>

<p>
The following is a more complicated example with nested box layouts.
</p>

<pre class="code">
using System;
using QtCore;
using QtGui;

/**
 * ZetCode Qyoto C# tutorial
 *
 * In this program, use box layouts
 * to create a windows example.
 *
 * @author Jan Bodnar
 * website zetcode.com
 * last modified October 2012
 */


public class QyotoApp : QWidget 
{
    public QyotoApp() 
    {
        WindowTitle = "Windows";

        InitUI();

        Resize(350, 300);
        Move(300, 300);
        Show();
    }

    void InitUI() 
    {
        QVBoxLayout vbox = new QVBoxLayout(this);

        QVBoxLayout vbox1 = new QVBoxLayout();
        QHBoxLayout hbox1 = new QHBoxLayout();
        QHBoxLayout hbox2 = new QHBoxLayout();

        QLabel windLabel = new QLabel("Windows", this);
        QTextEdit edit = new QTextEdit(this);
        edit.Enabled = false;

        QPushButton activate = new QPushButton("Activate", this);
        QPushButton close = new QPushButton("Close", this);
        QPushButton help = new QPushButton("Help", this);
        QPushButton ok = new QPushButton("OK", this);

        vbox.AddWidget(windLabel);

        vbox1.AddWidget(activate);
        vbox1.AddWidget(close, 0, AlignmentFlag.AlignTop);
        hbox1.AddWidget(edit);
        hbox1.AddLayout(vbox1);

        vbox.AddLayout(hbox1);

        hbox2.AddWidget(help);
        hbox2.AddStretch(1);
        hbox2.AddWidget(ok);
        
        vbox.AddLayout(hbox2, 1);

        Layout = vbox;
    }

    [STAThread]
    public static int Main(String[] args) 
    {
        new QApplication(args);
        new QyotoApp();
        return QApplication.Exec();
    }
}
</pre>

<p>
In this layout, we use two vertical and horizontal boxes. 
</p>

<pre class="explanation">
QVBoxLayout vbox = new QVBoxLayout(this);
</pre>

<p>
This is the base layout of the example. 
</p>

<pre class="explanation">
vbox.AddWidget(windLabel);
</pre>

<p>
First goes the label widget. It goes simply to the top of the
vertical box. 
</p>

<pre class="explanation">
vbox1.AddWidget(activate);
vbox1.AddWidget(close, 0, AlignmentFlag.AlignTop);
hbox1.AddWidget(edit);
hbox1.AddLayout(vbox1);

vbox.AddLayout(hbox1);
</pre>

<p>
In the center part of the window we have a text edit widget and
two vertically lined up buttons. The buttons go into a vertical box. The
buttons are aligned to the top within this vertical box. The vertical box
and the text edit go into a horizontal box. This horizontal box goes to the base
vertical box, just below the label widget. 
</p>

<pre class="explanation">
hbox2.AddWidget(help);
hbox2.AddStretch(1);
hbox2.AddWidget(ok);

vbox.AddLayout(hbox2, 1);
</pre>

<p>
The help and the ok buttons go into another horizontal box. There is 
an expanded white space between these two buttons. Again, the horizontal box
goes to the base vertical box. 
</p>

<pre class="explanation">
Layout = vbox;
</pre>

<p>
The base vertical box is set to be the main layout of the window. 
</p>

<img src="/img/gui/sharpqyoto/windows.png" alt="Windows example">
<div class="figure">Figure: Windows example</div>


<h2>New Folder example</h2>

<p>
In the last example, we use the <code>QGridLayout</code> manager to 
create a New Folder layout example.  
</p>

<pre class="code">
using System;
using QtCore;
using QtGui;

/**
 * ZetCode Qyoto C# tutorial
 *
 * In this program, use the QGridLayout manager
 * to create a New Folder example.
 *
 * @author Jan Bodnar
 * website zetcode.com
 * last modified October 2012
 */


public class QyotoApp : QWidget 
{
    public QyotoApp() 
    {
        WindowTitle = "New Folder";

        InitUI();

        Resize(300, 300);
        Move(300, 300);
        Show();
    }

    void InitUI() 
    {
        QGridLayout grid = new QGridLayout(this);

        QLabel nameLabel = new QLabel("Name", this);
        QLineEdit nameEdit = new QLineEdit(this);
        QTextEdit text = new QTextEdit(this);
        QPushButton okButton = new QPushButton("OK", this);
        QPushButton closeButton = new QPushButton("Close", this);

        grid.AddWidget(nameLabel, 0, 0);
        grid.AddWidget(nameEdit, 0, 1, 1, 3);
        grid.AddWidget(text, 1, 0, 2, 4);
        grid.SetColumnStretch(1, 1);
        grid.AddWidget(okButton, 4, 2);
        grid.AddWidget(closeButton, 4, 3);
    }

    [STAThread]
    public static int Main(String[] args) 
    {
        new QApplication(args);
        new QyotoApp();
        return QApplication.Exec();
    }
}
</pre>

<p>
In our example, we have one label, one line edit, one text edit and two buttons. 
</p>

<pre class="explanation">
QGridLayout grid = new QGridLayout(this);
</pre>

<p>
We create an instance of the <code>QGridLayout</code> manager. 
</p>

<pre class="explanation">
grid.AddWidget(nameLabel, 0, 0);
</pre>

<p>
We place the label widget in the first cell of the grid. The cells count from 0. 
The last two parameters are the row and column number. 
</p>

<pre class="explanation">
grid.AddWidget(nameEdit, 0, 1, 1, 3);
</pre>

<p>
The line edit widget is placed at the first row, second column. 
The last two parameters are the row span and the column span. Horizontally, the
widget will span three columns.
</p>

<pre class="explanation">
grid.SetColumnStretch(1, 1);
</pre>

<p>
The parameters of the method are the column number and the stretch factor.
Here we set stretch factor 1 to the second column. This means, that this column 
will take all remaining space. This was set, because we wanted our buttons to 
retain their initial size.
</p>

<img src="/img/gui/sharpqyoto/newfolder.png" alt="New Folder example">
<div class="figure">Figure: New Folder example</div>


<p>
In this part of the Qyoto C# tutorial, we have mentioned layout management of 
widgets. 
</p>

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